-f    Follow. If the input-file is not a pipe,  the  program
           will  not  terminate  after the line of the input-file
           has been copied,  but  will  enter  an  endless  loop,
           wherein  it  sleeps  for a second and then attempts to
           read and copy further  records  from  the  input-file.
           Thus  it  may  be used to monitor the growth of a file
           that is being written by some other process.

##</code><code>##

use IO::Select;
open (F, 'tail -f somefile.log |') or die;
$select = IO::Select->new(*F) or die "Unable to create select object";
while(<F>) {
   $lastrec = "matt: ".$_;
   print $lastrec;
   while (! $select->can_read(1)) {
      print $lastrec;
   }
}